function dataURLtoFile(dataurl, filename) {
  let arr = dataurl.split(','), mime = arr[0].match(/:(.*?);/)[1]
  let bstr = atob(arr[1])
  console.log(bstr)
  return bstr
}
dataURLtoFile('data:video/mp4;base64,aHR0cHM6Ly8xMjUyMjQ0MzEwLnZvZDIubXlxY2xvdWQuY29tLzkwODk2NzFmdm9kdHJhbnNnenAxMjUyMjQ0MzEwLzJmYTg0OGFjNTI4NTg5MDgwOTc4NDIxMDA0Ny92LmYxMDAwMzAubXA0')